get rid of command override in docker/test/docker-compose.yml

[amir-arad]

docker/test/docker-compose.yml overrides default command line of each container in order to customize confiuguration. It's cumbersome, as the main entry point should remain an implementation detail of the image.

Our images should read all necessary arguments from environment variables (and/or config files) to support this use case. and docker-compose config should use it.

see @netoneko 's comment on #1411